Frying Pan Lake – the Biggest Hot Spring in the World

8 October 2012

In 1886, Mount Tarawera, near the town of Rotorua on New Zealand’s North Island erupted. It was New Zealand’s largest volcanic eruption and it killed over a hundred people. It left behind a massive crater but nature had other plans for the place. Less than 130 years later New Zealand is the proud owner of the largest hot spring in the world.

The local Europeans quickly gave their new spring an it does what it says on the label name – Frying Pan Lake. Although it only fills part of the crater made by the 1886 flare-up of Tarawera, the lake, which has a flat bottom, has a depth of six meters but the vents leading up to it are often three times the size.

The magma is somewhere below it, close enough for a hydrothermal system to be created around the lake in the area known as Waimangu Volcanic Valley. Although the average temperature of the lake is around 50°C the hottest areas are almost boiling. As a result steam and various noxious gases are constantly released from Frying Pan Lake.

At the side of the lake is a natural formation which looks (and serves) like a big chimney. Around the edges of the lake blue/green algae proliferates. The orange color is the keratine they produce to protect themselves from the UV light.

The water is acidic with an average PH of 3.5 which means it must not be used as drinking water. The lake looks as if it is constantly boiling but it is the gas, mostly carbon dioxide and hydrogen sulphide, which mostly give it that appearance.

Yet there is real boiling going on, under the water where the vents on the lake bed release water which is truly scorching. Evaporation, convection and radiation of heat ensure that it is much cooler when it hits the surface.

All told Frying Pan Lake covers an area of 38,000 square meters and is fed by an uncounted number of acid springs. Considering the lake was made only yesterday it is surprising how the native forest grows down almost to the very edge of the biggest hot spring in the world.